1NJTJEIOUS TO MAN. 269 



washing races of mankind, by serving as a succedaneum 

 for soap and water, and, by the irritation which they 

 cause, keeping up a healthy action of the skin. 



As to secondarily noxious insects, a savage nas no con- 

 ception of them. He does not till the earth, and conse- 

 quently has no crops to be devoured. He possesses 



